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Pentachlorophenol is an old-line pest control agent that came under regulatory pressure decades ago. Beginning in the 1930s, it was used as an insecticide (including for termite control), a defoliant for crops before they were harvested, a wood preservative (notably in telephone poles), and a biocide with numerous other agricultural and industrial uses.
Pentachlorophenol is made by chlorinating phenol at high temperature. In the commercial process, chlorination is incomplete, and the product contains even more toxic impurities such as dibenzo-p-dioxin derivatives. The compound鈥檚 odor is similar to that of benzene or phenol; it is sparingly soluble in water and slow to decompose in nature.
Pentachlorophenol鈥檚 pervasive toxicity and environmental threats (see the hazard information table) doomed it to severe use restrictions by the 1980s. Today, wood preservation is the only use permitted by the US Environmental Protection Agency. Earlier this year, the . The comment period for this proposal expired in May, and EPA is currently proceeding with canceling the registration
For additional information, see .
Pentachlorophenol hazard information
| Hazard class* | GHS code and hazard statement | |
|---|---|---|
| Acute toxicity, oral, category 3 | H301鈥擳oxic if swallowed |  |
| Acute toxicity, dermal, category 3 | H311鈥擳oxic听 in contact with skin | |
| Skin corrosion/irritation, category 2 | H315鈥擟auses skin irritation |  |
| Serious eye damage/eye irritation, category 2A | H319鈥擟auses serious eye irritation | |
| Acute toxicity, inhalation, category 2 | H330鈥擣atal if inhaled | |
| Specific target organ toxicity, single exposure, respiratory tract irritation, category 3 | H335鈥擬ay cause respiratory irritation | |
| Carcinogenicity, category 2 | H351鈥擲uspected of causing cancer |  |
| Short-term (acute) aquatic hazard, category 1 | H400鈥擵ery toxic to aquatic life |  |
| Long-term (chronic) aquatic hazard, category 2 | H411鈥擳oxic to aquatic life with long-lasting effects | |
*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals.听
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Pentachlorophenol
fast facts
| CAS Reg. No. | 87-86-5 |
nomenclature | Phenol, 2,3,4,5,6-pentachloro- |
| Empirical formula | C6HCl5O |
| Molar mass | 266.34 g/mol |
| Appearance | White crystals or powder |
| Melting point | 191 掳C |
| Water solubility | 14 mg/L |
MOTW update
Nitrous oxide (N2O) was the Molecule of the Week for January 14, 2013. It is the third-most-emitted climate change contributor, after carbon dioxide and methane, yet little has been done to curtail it. Now, pressure from government agencies and environmental groups is forcing the chemical industry worldwide to install equipment .
MOTW update:
February 21, 2022
Pentachlorophenol听is an old-line insecticide and wood preservative that is a 鈥渞easonably anticipated鈥� human carcinogen and an environmental hazard.
After decades of restricting the use of pentachlorophenol, the US Environmental Protection Agency proposed a complete ban on it in early 2021. This month, EPA , which will go into effect in 2024. Wood-treatment companies are permitted to use up existing stocks until 2027.
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